<!DOCTYPE html>
<html>

<head>
    <meta charset="utf-8">
    <title>菜鸟教程(runoob.com)</title>
    <style>
        /* unvisited link */
        a:link {
            text-decoration: none;
        }

        /* visited link */
        a:visited {
            text-decoration: none;
        }

        /* mouse over link */
        a:hover {
            text-decoration: underline;
        }

        /* selected link */
        a:active {
            text-decoration: underline;
        }
    </style>
</head>

<body>
    <p><b><a href="/css/" target="_blank">This is a link</a></b></p>
    <p><b>注意:</b> hover必须在:link和 a:visited之后定义才有效.</p>
    <p><b>注意:</b>active必须在hover之后定义是有效的.</p>
</body>

</html>